Management and Evaluation of Large Scale Water System for Sustainable Agriculture Development and for Envilonment Maintenance.

广泛分布于流域的大型水系管理具有流域回用机制的特点。利用该机制实现了水的有效利用。在本研究中，(1)分析了具有不同条件的几个水系统的水利用模式，(2)阐明了系统中水利用模式的水质变化过程。通过对不同条件下农村环境养护的研究，提出了合理的水资源管理技术。对Kasagawa盆地（溪区）、Kasumigaura地区（闭水盆地和水田区）、Shinanogawa盆地（低洼水田区）、Ishikarigawa盆地（宽水田区）和Sendaigawa盆地（窄倾斜区）进行了实地调查和实验分析。在综合考虑各区域水质的基础上，考察了水管理的特点，指出了影响水管理的因素。特别是通过理论和实验分析，阐明了(1)系统中水的循环速度（系统中水的回用率）与(2)溶解氧、总氮、总磷酸盐等水质指标之间的动态关系。本研究取得的成果已在多家期刊上以论文形式发表。

Managements of large water system widely spreading in river basin is characterized by the reuse mechanism of return flow in the basin. The effective water use is performed using the mechanism.In this research, (1) water use patterns were analyzed for several water systems having various conditions, and (2) the changing process of water qualities were clarified concerning water use patterns in the systems. Several technics on reasonable water management were proposed as the results of the research for keeping environmental maintenance in rural areas having various conditions.Field surveyings and experimental analyzings were carried out for several areas i. e., The Kasagawa Basin (creek area), The Kasumigaura District (closed water basin and paddy area), The Shinanogawa Basin (low lying paddy area), The Ishikarigawa Basin (wide paddy area) and The Sendaigawa Basin (narrow & inclined area). The characteristics of water management were examined and the factors affecting the water managements were pointed out with considering the water qualities for each area. Particularly, theoretical and experimental analyzes for clarifying the dynamic relationships between (1) cyclic velosity of water in the system (the reuse ratio of water in the system) and (2) water quality indexes such as dissolved oxygen, total nitrogen, total phosphate and so on.The obtained results concerning this research were published as original papers in several journals.